Fears surrounding a potential trade war between the U.S. and other major economies continue to plague market sentiment around the world.

NEW YORK (StockMarketNews.Today) - U.S. stock index futures slumped on Monday, the first trading day of the third quarter.

The Trump administration is reportedly looking into drafting a bill that would allow the White House to unilaterally increase trade tariffs without congressional consent, according to an Axios report published Sunday. If legislation moves ahead, it could mean that the U.S. would be acting outside of the World Trade Organization’s policies and rules.

Elsewhere, a report by the Financial Times suggested that the U.S. could receive a new round of tariffs worth as much as $300 billion, if Washington moves ahead with levies on automakers in the European Union.

Monday also marked the first trading day of the second half of the year. Equities posted mixed performances in the first half, with Nasdaq composite and S&P 500 rising 8.8 percent and 1.7 percent, respectively, while the Dow declined 1.8 percent. The small-caps Russell 2000, meanwhile, rose 7 percent to start off 2018.

On Saturday, President Donald Trump tweeted that he’d asked King Salman of Saudi Arabia for the country to pump more oil “maybe up to 2,000,000 barrels, to make up the difference” and that he had agreed. The White House, however, have since walked back on the president’s comments.